hwset4solution

# The rst term will be blocked by the if lter and the

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Unformatted text preview: ωRF are applicable in this case. If the signals are summed at the output of the mixer then according to equation 1 the output will be zero. If the signals are diﬀerenced, then according to equation 2 the output will be A cos[(2ωc + ωIF )t] + A cos(ωIF t). The ﬁrst term will be blocked by the IF ﬁlter, and the second term will be passed. Thus, we should use the − sign in the combiner in order to produce the desired frequency conversion. d. The image signal is at ωRF = ωc + 2ωIF . For the image signal, ωLO < ωRF , so if the signals are summed the output will be A cos(ωIF t). If the signals are diﬀerenced the output is A cos[(2ωc + 3ωIF )t]. Thus, when the signals are diﬀerenced, as required to produce the required output when the desired signal is input to the mixer, the image signal produces a ﬁnite output from the mixer, but the frequency of the output signal will be much higher than ωIF . Hence the response due to the image signal is easily rejected by the IF ﬁlter, so the image signal will not produce any output after the IF ﬁlter. 2...
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## This homework help was uploaded on 03/13/2014 for the course ECE 453 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.

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